Protests erupted in Uganda's capital on Friday after police blocked a pop star-turned-opposition lawmaker from leaving for the United States for treatment after alleged torture.

The action by security forces has escalated a political dispute between the government of longtime President Yoweri Museveni and a youthful generation that fears he intends to rule for life after 32 years in power.

Bobi Wine, whose real name is Kyagulanyi Ssentamu, was stopped Thursday night while trying to board a flight at the Entebbe airport, lawyer Asuman Basalirwa told The Associated Press. He was checked into a hospital in the capital, Kampala, in a "worrying condition," the lawyer said.

The 36-year-old had been freed on bail on Monday but faced no travel restrictions after he and several other lawmakers were arrested and charged with treason over an incident in which the president's motorcade was pelted with stones and Ssentamu's driver was shot dead. A lawyer for the singer has called the charge false.

Kenyan activists and civil society groups protest
Kenyan activists and civil society groups protest in solidarity with Ugandan pop star-turned-lawmaker Kyagulanyi Ssentamu, also known as Bobi Wine, in a march to the Ugandan embassy in Nairobi, Kenya, Aug. 23, 2018.

Ssentamu has emerged as a powerful opposition voice among youth frustrated by Museveni, especially after the constitution was changed last year to remove an age limit on the presidency. The singer won a parliament seat last year without the backing of a political party.

Dozens of global musicians including Chris Martin, Angelique Kidjo and Brian Eno last week issued an open letter condemning the treatment of Ssentamu, who in his first public appearance after his arrest had to walk with support and appeared to cry.

On Thursday, police "violently abducted" Ssentamu and put him into a police ambulance, another lawyer, Nicholas Opiyo, said on Twitter. Ssentamu's wife, Barbara, said in a Facebook post that security forces "manhandled" her husband, who "groaned in pain" as he shouted for help.

Uganda police said Ssentamu had been taken to a hospital "for a medical examination as he alleged torture."

Authorities earlier on Thursday prevented another lawmaker, Francis Zaake, from boarding a plane to India, saying he was a suspect in a criminal case. Government spokesman Ofwono Opondo said Zaake, who has not been charged with any crime, escaped police custody "and should be arrested at the earliest."

After the outcry over Ssentamu's treatment at the airport, Opondo said both he and Zaake can travel "after government doctors have examined them to ascertain their medical conditions."

Both Ssentamu and Zaake on Friday were resisting efforts by government-provided medical personnel to examine them, according to local rights group Chapter Four Uganda, which urged medical professionals not to treat the lawmakers without their consent.

Both men had been hospitalized with serious injuries they said they sustained at the hands of security forces during detention.

The government has denied the allegations of torture.

Ssentamu is said to be suffering a kidney problem, according to his legal team, which cited a medical report by the hospital where he had been hospitalized.

The treason charges against Ssentamu and others have heightened concerns about a crackdown on the opposition in this East African nation and led to protests in the capital.

The 74-year-old Museveni, a close U.S. security ally, has held power since 1986. He has spoken in recent days about "unprincipled politicians taking advantage of our unemployed youth to lure them into riots and demonstrations."